1. Field of the Invention:
The invention relates to display systems and more specifically to raster scan display systems providing means for the relocation of overlapping elements without interference.
2. Description of the Prior Art:
In typical prior art raster scan systems displayed images were relocated by deleting (erasing) the image to be relocated and redrawing (writing) the image to be relocated at the new location. If the deleted portions overlapped one or more other images, all these images were erased. This was due to the fact that the raster scan system itself did not contain any capability of indicating the number of overlapping images which were being displayed at a particular position in the final display. Generally, these systems were associated with a computer which, through the use of software routines, kept track of the number of overlapping display images so that after a particular image was deleted during a relocation operation the images which were erased but not relocated could be restored. Such an arrangement had the disadvantages of being both relatively complicated from a software standpoint with image relocation being relatively slow. These problems are substantially reduced by the display system which is the subject of this invention.